Prahlad J. Purohit wrote:
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"20mA is too much without a buffer"



not for an AT89cx051.

Datasheet states that these devices have direct LED driving capability and each pin can sink up to 20 ma safely as far as a single pin is concern. But datasheet imposes another limit stating that, the sum of the output currents for all the outpts, should not be greater than 80 ma.



Abhishek